1. Field of the Invention
The present invention relates to a refrigerant transporting hose, particularly one that is improved not only in softness and resistance to the permeation of refrigerants but also in vibration and sound absorbing characteristics.
1. Description of the Related Art
A chlorofluorocarbon gas CFC-12 has long been used as a refrigerant in air conditioners on automobiles and so forth but being a causative agent of ozone depletion, CFC-12 was recently singled out as a substance the use of which must be regulated in order to conserve the environment on the earth. Under these circumstances, the use of hydrofluorocarbon HFC-134a as a substitute refrigerant is gaining popularity.
In conventional automotive air conditioners and so forth that use CFC-12 as a refrigerant, hoses made of NBR rubbers have been used to transport and supply the refrigerant to various parts of the machine. Such hoses are useful for transporting CFC-12 as the refrigerant but not suitable for use with HFC-134a on account of its undesirably high permeation. Under these circumstances, the refrigerant HFC-134a is conventionally transported by way of a hose that has a polyamide layer provided as the innermost layer in contact with the refrigerant. Another proposal is the formation of an inner tube from a rubber layer made of a rubber composition based on a butyl or halogenated butyl rubber [Unexamined Published Japanese Patent Application (kokai) No. 140688/1991)].
However, polyamides generally have high Young's moduli and are not satisfactory in softness; hence, if they are used as the constituent material of hoses for supplying refrigerants in automotive air conditioners and so forth, the vibrations and sound generated from the compressor cannot be effectively absorbed but are simply transmitted to other parts or, alternatively, the hose itself will vibrate to upset quietness. On the other hand, the hose of which the inner tube is formed from a rubber layer made of a rubber composition based on a butyl or halogenated butyl rubber does not have satisfactory resistance to the permeation of refrigerant HFC-134a.